In the related art, as a piezoelectric element, an element in which a piezoelectric body layer, which is formed from a piezoelectric material, is interposed between two electrodes is general, and piezoelectric elements are widely used as ultrasonic wave transmission elements and ultrasonic wave reception elements in ultrasonic wave measurement apparatuses, and bending vibration mode actuator devices in liquid ejecting heads. It is possible to include lead zirconate titanate (PZT) as a representative example of a piezoelectric material used in this kind of piezoelectric body layer (refer to JP-A-2001-223404). PZT fundamentally has a rhombohedral crystal structure, and is configured to exhibit a piezoelectric characteristic (an amount of strain) through the induction of an electric dipole moment as a result of the application of an electric field.
Meanwhile, in piezoelectric materials, a piezoelectric material that uses so-called 90 degree domain rotation that differs from the abovementioned theory, is well known. This piezoelectric material, for example, applies an electric field to a crystal, which is tetragonal, and in which an a axis component, a b axis component, and a c axis component are mixed, and is configured to exhibit a piezoelectric characteristic (an amount of distortion) as a result of the a axis component and the b axis component being rotated by 90 degrees at the c axis component.
However, in recent years, there has been a situation in which further increases in density and increases in performance have been desired in liquid ejecting heads, and there is a problem in that even in piezoelectric body layers in which displacement is caused using 90 degree domain rotation or the like, an improvement is desired in a piezoelectric constant. Additionally, in terms of achieving an improvement in a piezoelectric characteristic by improving a piezoelectric constant, since a circumstance in which displacement is hindered by the piezoelectric body layer itself is suppressed when the rigidity of the piezoelectric body layer is low, it is advantageous if the Young's modulus of the entire piezoelectric body layer can be reduced. These matters are also present in the same manner in piezoelectric elements that are used in applications other than liquid ejecting heads.
Accordingly, it is an object of the present invention to provide a piezoelectric element, a piezoelectric actuator device, a liquid ejecting head, a liquid ejecting apparatus, and an ultrasonic wave measurement apparatus that can improve a piezoelectric constant of the piezoelectric body layer.